Elevators typically are maintained in position and alignment by using a plurality of guide rails which are bolted to the elevator shaft. Guide shoes fixed to the elevator car ride on these rails keeping the car in position.
In the past, most guide rails had a T-shaped cross section. The head of the T is bolted to the building structure and some type of guiding mechanism on the elevator car rides on the stem of the T holding the elevator in place. These types of elevator guide rails are generally shown, for example, in Lindquist U.S. Pat. No. 1,566,490, Klein U.S. Pat. No. 4,271,932 and Blase U.S. Pat. No. 3,032,377.
This system functions well, but the T-shaped guide rails are relatively expensive. To reduce cost, elevator guide rails having a generally cylindrical configuration have been employed. These are commonly referred to as omega guide rails because the actual configuration is that of the Greek letter omega.
The guiding mechanism used with omega rails includes a set of three guide shoes which ride on each rail surrounding the rail. These are held by compressive force between the guide rail and shoe brackets. The shoe brackets are bolted to the elevator. Bosses or projections on the back portion of the guide shoe extend through apertures in the bracket thereby holding the shoes in place relative to the brackets. The apertures are larger than the bosses allowing for some movement. This movement is required because the guide rails are not absolutely straight.
FIG. 1 shows a perspective view of one of these prior art guide shoes. It has an arcuate, front rail engaging surface 11 and a planar back surface 12 with projections or bosses 13 and 14 extending from the back portion.
Very strong compressive forces are required to hold these guide shoes in position between the rail and bracket. Because of these strong compressive forces, when the shoe moves relative to the bracket, it snaps, creating a very loud noise. This tends to frighten elevator passengers. For this reason, the more expensive T-shaped guide rails are preferred over the omega rails regardless of the added expense.